2-3 hours. I should add I have only been taking it a week so far and am liking the fact it doesn't seem to cause the side effects as others do. I'm going back to the Dr. tomorrow and was wondering if anyone had any suggestions, as at this point it's too short acting and doesn't seem to get the pain level down to even a comfortable level. This is all I'm taking at this point for the pain as well as Soma's 3x day which I don't think does anything.